Highly compressive gun system comprising a combined electrostatic and magnetic focusing



p 1961 w. KLEIN ET AL 3,001,095

HIGHLY COMPRESSIVE GUN SYSTEM COMPRISING A COMBINED ELECTROSTATIC AND MAGNETIC FOCUSING Filed Feb. 12, 1958 Fig. 7

WMIIJIIIII 5 'IIIIIIIIIIIIIIJ Fig- 2 INVENTORS \MKlein'wFriz ATTORNEY 3,001,095 EHGHLY COMEPRESSTVE GUN SYSTEM MPR- ENG A CQMBINED ELECTROSTATIC AND MAT NETIC FUCUSING Werner Klein, Korntal, Germany, and Walter Friz, Fairhorn, Ghio, assignors to Q Lorenz Ahtiengeseiischaft, fituttgart-Zufienhausen, Germany, a corporaticn of Germany Filed Feb. 12, 1958, Ser. No. 714,789 Claims priority, application Germany Feb. 15, 1957 ll Claim. (Cl. 31384) When employing highly compressive gun systems, also known as beam generating systems, it has recently become known to use a combined electrostatic and magnetic cornpression. A purely electrostatic compression, as was hitherto used for generating a so-called Brillouin beam, bears different disadvantages, such as increased noises, high sensitivity of the gun system against build-in tolerances, a strong dependency of the amplification upon the magnetic field intensity or strength, and a dropping output power as the magnetic focusing field intensity increases, as well as a strong increase of the helix loss current in the case of an increasing input signal up to near the saturation range of the tube. Gun systems comprising a combined electrostatic and magnetic compression, however, are not featured by these deficiencies and still bear the added advantage of having a higher efficiency as well as a more exact beam guidance caused by a more intensive coupling.

A gun system comprising a combined electrostatic and magnetic compression may be realized in different ways; for example, around the gun system there may be arranged a magnetic shielding jacket, the opening of which is so designed that a certain portion of the magnetic field, which is necessary for the focusing of the electron beam, is eifective in the cathode plane, and that the field intensity gradually increases from the cathode plane up to the full value of the magnetic field intensity. In the case of a smaller compression it is suflicient to obtain the desired increase in field intensity by means of specially designed ferromagnetic rings. The large angles of convergency in the electromagnetic focusing field which are necessary in the case of highly compressive gun systems, however, cannot be obtained with the aforementioned type of gun system. In the case of a very high compression there usually appear unavoidable distortion errors which are the cause of the desired intersecting point of the electron beams being enlarged to an intersecting area. For still obtaining a useful focusing in spite of these unavoidable distortion errors, the invention proposed to design the shielding for the magnetic field in such a way that by means of a further increase of the guide field intensity there will be maintained a further convergenc y of the guide field within the range or area of intersection. In accordance with the invention this may be accomplished in that the magnetic shielding means (jackat), as seen from the cathode, consists with respect to rotation-symmetrical systems of circular cylindrical zones of an increasing diameter, or is formed in the case of flat beams by a ferromagnetic structure of a trough-shape which, as seen from the cathode, is expanded or widened out in a step-like manner. The limiting area or surface of these bodies is determined by the magnetic guide field.

According to a further feature of the invention it is proposed to design the shielding means or shielding jacket as a double screen, so that for instance there is provided one shielding jacket inside the vacuum tube, while a second one is arranged outside the vacuum tube. By the separation of these two screens they may be applied to a difierent magnetic potential. By the distance or space Patented Sept. 19, 1961 between both screens as well as by a certain overlapping there are also provided the necessary degrees of freedom. One particular advantage of this embodiment resides in the fact that it is possible to compensate the always appearing variations of the values by means of a simple readjustment of the outer screen.

FEGURE 1 discloses an electron gun system having a unitary shielding screen jacket; and

FIGURE 2 discloses an electron gun system having a double shielded screen jacket.

in FIG. 1 there is schematically shown a gun system of the high-compression type comprising a combined electrostatic and magnetic focusing, wherein the concave cathode 1 is surrounded by the focusing electrode 2, and in which system there is provided an acceleration anode 3. A ferromagnetic shielding jacket 4 surrounds this gun system, and a further portion 5 of this shielding jacket is adapted to render possible the aforementioned additional increase in field intensity. The gun system itself including the magnetic shielding jacket is arranged in a homogeneous guide field of the total flux 5.

In FIG. 2 there is schematically shown a gun system with a double screen. The concave cathode 1 is also in this case surrounded by a focusing electrode 2. There is provided a special accelerating anode 3. The gun system is enclosed by a ferromagnetic shielding jacket 4. A further screen 6, overlapping the screen 4 by a certain amount takes care not only of a predetermined spacing from the screen 4, but also of the additional increase in field intensity.

It is appropriate to arrange the vacuum envelope between the shielding screeus 4 and 6. The screen 6 will then become adjustable from the outside; in this way at a given total flux there may be adjusted the most optimum amount of increase of field intensity.

With the aid of these two examples of embodiment of the invention it is rendered possible to construct gun systems with a combined electrostatic and magnetic compression, having a particularly high degree of compression, whereby the angle of convergency may be greater than 30.

While we have described above the principles of our invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention as set forth in the objects thereof and in the accompanying claim.

What is claimed is:

A highly compressive gun system for producing a beam in a predetermined direction having electrostatic focusing means including a cathode, an accelerating anode and magnetic focusing comprising a first substantially cylindrical shield portion of a given diameter surrounding said gun throughout its length and terminated substantially at the anode, and a second substantially cylindrical shield portion of a larger diameter parallel to and surrounding said first shield portion and extending beyond said first shield portion in a direction of the beam.

References Cited in the file of this patent UNITED STATES PATENTS 2,522,872 Heppner Sept. 19, 1950 2,619,607 Steers Nov. 25, 1952 2,812,467 Kompfner Nov. 5, 1957 2,828,434 Klein Mar. 25, 1958 2,876,378 McDowell Mar. 3, 1959 FOREIGN PATENTS 60,887 Belgium Apr. 15, 1948 1,075,900 France Oct. 20, 1954 

